1. Field of the Invention
The present invention relates to a method for purifying aqueous dye solutions. More particularly, the present invention provides a high purity water-soluble dye for use as a coloring component of a recording agent. The recording agent can be used, for example, in an ink-jet recording system or a manual writing implement (hereinafter, the recording liquid is referred to as "ink").
2. Description of the Prior Art
Water-soluble dyes such as direct cotton dyes, acid dyes, basic dyes, reactive dyestuffs and the like have conventionally been used for the dyeing of fibers, woven cloths, etc. Further, these dyes are recently used as coloring components in ink jet recording wherein an ink is discharged by various discharging means to form ink droplets and the ink droplets are deposited to a recording medium such as a paper or the like in accordance with image signals. Furthermore, the water-soluble dyes are used as coloring components of inks used in writing, such as fountain pen, felt tip pen, ball point pen and the like.
As coloring component dyes of inks, particularly inks which are used in ink jet recording, there are generally utilized dyes for dyeing of fibers. These dyes contain large amounts of additives or impurities. Therefore, when such commercially available dyes are used for ink jet recording, the inks cause various troubles. One of the most serious is clogging of the ink-discharging orifice, and another is deposition of impurities on the heat-generating head in the ink jet recording method utilizing heat energy for ink discharge. In order to prevent such troubles, purification of dyes used in these inks have heretofore been proposed and carried out. Accordingly, some improvements have been achieved and problems caused by inks have been reduced by using dyes of higher purity. However, there still exists a phenomenon that inks which are pure after production, when delivered from ink manufacturers and stored for several months or years, frequently cause unanticipated problems. These troubles are significant particularly in the ink jet recording method employing heat energy for ink discharge.